Insulator element and manufacture thereof



9 s. H. STUPAKQFF ET AL. w m

INSULATOR ELEMENT AND MANUFACTURE THEREOF Filed April 16, 1950 Patented Oct. 1, 1935 UNITED STATES PATENT OFFICE INSULATOR ELEMENT AND MANUFACTURE THEREOF Delaware Application April 16, 1930, Serial No. 444,796

5 Claims.

This invention relates to the manufacture of insulators and more particularly to insulators used as the heater wire support in alternating current radio tubes.

Insulator supports as heretofore generally constructed have consisted of a refractory rod of small diameter having two continuous parallel holes therethrough. This rod is cut into lengths and a hairpin-shaped heater wire is inserted in the length of rod, one length of the wire extending through each of the holes. This type of heater is objectionable for the reason that there is a relatively large mass of refractory material to be heated in comparison with the size of the heater wire so that a very appreciable interval of time is required for a radio tube equipped with such a heater to reach anoperating temperature after the current is turned on. Also the wire, which is very fragile, is confined throughout its entire length by the refractory, and in expanding and contracting the whole length of the wire is subjected to the abrading action of the refractory. It has been proposed to use insulators in which the heater wire is exposed throughout the greater portion of its length, but heretofore the insulators have not been constructed in such a way as to permit their use on a commercial scale.

According to the present invention, an insulating support is made in accordance with a method which is both cheap and practical and the heater wire is exposed throughout the greater portion of its length. The invention may be readily understood by reference to the accompanying drawing in which,

Figure 1 is a perspective View on a very greatly enlarged scale of an insulating support embodying one form of our invention;

Figure 2 is an exploded view showing the manner of assembling the support;

Figure 3 is a view similar to Fig. 1 of a slightly modified construction;

Figure 4 is a view similar to Fig. 2 showing the manner of assembling the structure illustrated in Fig. 3;

Figure 5 is a front elevation of an extruding die member for forming a part of the insulator shown in Figs. 3 and 4;

Figure 6 is a longitudinal sectional view through the extruding die;

Figure '7 is a View similar to Fig. 1 of still another support; and

Figure 8 is a somewhat diagrammatic view illustrating the manner of shaping the support.

In the construction shown in Fig. 1 the insulating support designated generally as 2 comprises a rod member 3 having spaced apart collars l thereon, these collars being cemented or otherwise suitably secured in place on the rod.

The collars or sleeves 4 are of uniform internal 5 diameter. The sleeve, however, is provided along two diametrically opposite sides with small grooves 5.

In forming the insulating support the rod 3 with its wire receiving grooves 5 is extruded from 1 a plastic or semi-plastic mix through an extruder of a type familiar to those skilled in the art, this rod being originally of any convenient length. It is then cut up into sections of the length desired for the support. The collars 4 are also cut 15 from a length of extruded refractory tubing. A cement or bonding agent is then applied to the rod 3 at suitable points, or to the insides of the sleeves 4, or to both, and the sleeves are slipped on the rods to form the completed support. The 20 looped heater wire which is subsequently applied to the support is accommodated by the grooves 5 in the sides of the rod 3, these grooves providing clearance to permit the insertion of the wire through the sleeves 4. Due to the simple shape 25 of the dies for forming this insulator and the ease with which the parts can be assembled, the insulator can be made quite cheaply.

The arrangement shown in Figs. 3 and 4 is somewhat the reverse of the arrangement de- 30 scribed in connection with Figs. 1 and 2. In this embodiment of the invention the insulator support comprises a main rod member 6 which is fiat along two opposite sides, or is substantially rectangular in cross-section, although the nar- 35 rower edges may be rounded as shown in Fig. 4. Placed along the rod 6 are sleeve members I. These sleeve members, shown in detail in Fig. 4, have a central longitudinally extending opening 8 with a small semicircular recess or groove 40 extending along two of the side walls thereof, these grooves being designated 9. The sleeves I are slipped onto the supporting rod 6 and cemented in place. The grooves 9 provide an opening through the sleeves 1 at each side of the rod 6 through which the heater wire may be passed.

By reason of the opening 8 being substantially rectangular in cross-section and the rod 6 being substantially rectangular in cross-section, it will 50 be seen that when the sleeves I are slipped onto the rod 6 the grooves 9 of the successive collars must always accurately line up. This structure, like the one shown in Fig. 1, can be manufactured on a commercial scale, and allows the heat- 55 

